This invention relates to the extrusion of a multi-layer plastic pipe. In one aspect, this invention relates to the extrusion of pipe having an ultraviolet light-protective outer surface and a light-reflecting inner surface. In another aspect, this invention relates to a method and apparatus for the extrusion of a multi-layer pipe.
In the maintenance of large diameter plastic pipes, (e.g., generally up to about 48 inches in diameter) such as water lines and sewer drainage piping or the like, it is in many cases required that a utility surface inspection thereof include video viewing and/or recording of the interior of the pipe. Traditionally, such pipes have been made utilizing a black, high density polyethylene (HDPE) because of the black HDPE pipe's excellent resistance to deterioration due to ultraviolet light. However, the black interior of the black HDPE pipe makes it unsuitable for video inspection of the interior due to the light absorption properties of the black color.